This invention relates to a semiconductor laser. More particularly, it is concerned with a polarization-switchable semiconductor laser.
Optical modulators and especially switches are important components for optical communications and optical data transmission. Conventional optical polarization switching is achieved by electro-optic or acousto-optic modulation of light waves. An electro-optic polarization switch changes the polarization of light waves in response to an electrical signal applied to a passive material through which light is propagating. The acousto-optic effect changes the optical property of a passive material by mechanical strains induced by the passage of an acoustic wave. In both cases, the switching is limited by the speed of the externally applied electrical or acoustic signal. The electro-optic switches have advantages over the acoustooptic devices and are the most commonly used passive switching devices at the present time. However, in order to switch the polarization of light from the transverse electric (TE) mode to the transverse magnetic (TM) mode or vice versa, a large electric field of the order of 10 kV/cm is generally needed.